telemetry: fix spurious 'Failed to detach context' error on shutdown

src/rhapsody/telemetry/manager.py

@@ -176,9 +176,13 @@ def __init__(
         # correct parent span context in the dispatch loop.
         self._task_contexts: dict[str, Any] = {}
 
-        # Token returned by context.attach() when the session span is activated in start().
-        # Stored so it can be properly detached in stop().
+        # Token returned by context.attach() when the session span is activated in start(),
+        # plus the asyncio task that performed the attach. ContextVar tokens can only be
+        # reset from the contextvars.Context they were created in (i.e. the same task), so
+        # stop() skips the detach when it runs in a different task — OTel would otherwise
+        # log a spurious "Failed to detach context" ValueError at shutdown.
         self._session_ctx_token: Any = None
+        self._session_ctx_task: Any = None
 
         # Caller-supplied OTel extension points wired into RHAPSODY's internal providers
         # at start() time alongside SpanBuffer / InMemoryMetricReader.
@@ -251,6 +255,7 @@ async def start(self) -> None:
         self._session_ctx_token = otel_context.attach(
             trace_mod.set_span_in_context(self._session_span)
         )
+        self._session_ctx_task = asyncio.current_task()
 
         self._running = True
         self._dispatch_task = asyncio.create_task(self._dispatch_loop(), name="telemetry-dispatch")
@@ -322,8 +327,15 @@ async def stop(self) -> None:
         from opentelemetry import context as otel_context
 
         if self._session_ctx_token is not None:
-            otel_context.detach(self._session_ctx_token)
+            # Detach only when stop() runs in the task that attached the token in
+            # start(); a token reset from any other task raises ValueError inside
+            # otel_context.detach(), which OTel catches and logs as an ERROR.
+            # Skipping is safe: the attach only ever affected the starting task's
+            # context, and the tracer provider shuts down right below.
+            if asyncio.current_task() is self._session_ctx_task:
+                otel_context.detach(self._session_ctx_token)
             self._session_ctx_token = None
+            self._session_ctx_task = None
 
         if self._meter_provider:
             self._meter_provider.shutdown()